1. Field of the Invention
This invention relates to the production of microparticles, more particularly to a method for producing microparticles of a dispersed phase liquid in a continuous phase liquid.
2. Description of the Related Art
Application of biotechnology has been widely extended to many industrial fields, such as cosmetic and food industries in addition to the manufacture of pharmaceutical products. For example, microparticles have been produced based on biotechnology for nutritious foods in order to improve absorption of the nutritious foods by human bodies. Many methods and apparatuses have been suggested in the art for the production of microparticles.
Referring to FIGS. 1, 2 and 3, U.S. Pat. No. 6,177,479 discloses an apparatus for producing microspheres, which includes a housing 10 and a forming unit 20. The housing 10 includes a receiving space 11, and first, second and third channels 12, 14 and 16 all of which are connected to the receiving space 11.
The forming unit 20 is rectangular and includes opposite first and second faces 21 and 22. The first face 21 is recessed to form a rectangular recess 210, and a through hole 23 extends through the center of the first and second faces 21, 22 and the center of the recess 210. A row of protrusions 251 are spaced apart by microgaps and are formed on one of sidewalls 25 which surrounds the rectangular recess 210. The first face 21 is placed in contact with a wall surface of the receiving space 11 so that the second channel 14 is communicated with the through hole 23 and the rectangular recess 210.
In use, a first liquid is introduced into the first channel 12, whereas a second liquid is directed to the second channel 14. The first liquid flows into and fills the receiving space 11, and the second liquid flows through the through hole 23. After the rectangular recess 210 is filled, the increasing pressure in the recess 210 due to the continued inflowing of the second liquid will cause the second liquid to squeeze through the microgaps of the protrusions 251, thereby forming microspheres which are then dispersed in the first liquid in the receiving space 11.
In the aforesaid system, a surfactant is added to the second liquid in order to stabilize the microspheres of the second liquid in the first liquid. However, the aforesaid system requires a high pressure to pressurize the second liquid in the rectangular recess 210 and a tight fluid seal between the forming unit 20 and the housing 10. Otherwise, the second liquid can flow through other gaps than the microgaps, resulting in non-uniform liquid particles and/or failure to form microspheres.
Furthermore, since the size of the microspheres depends on the size of the microgaps, it is impossible to vary the size of the microspheres once the microgaps have been designed and constructed.
Other examples of the microsphere production are disclosed in U.S. Pat. Nos. 6,258,858, 6,576,023, 6,155,710 and 6,387,301.
U.S. 2005/0274423 A1 discloses several capillary chips used for mixing and reacting a sample with reagents. In FIG. 1A, a sample and a first reagent are mixed to undergo a reaction downstream of a junction P1 of two channels 31 and 32, a second reagent is mixed with the sample downstream of another junction P2, and a final reaction is completed at a position P3. Time period of the reaction of the sample with the first or second reagent is adjusted by making a valve part V1 in a closed state. This publication suggests nothing relating to the production of microparticles from immiscible liquids, such as a continuous phase liquid and a dispersed phase liquid.
U.S. 2001/0033796 A1 discloses various microfabricated elastomeric valve and pump systems for controlling microflows in microchannels. FIG. 27of this publication illustrates a multiplexing system adapted to selectively permit fluid to flow through selected channels. This publication also suggests nothing relevant to the production of microparticles from immiscible liquids.